/* Copyright (c) 2014, ENEA Software AB
 * Copyright (c) 2014, Nokia
 * All rights reserved.
 *
 * SPDX-License-Identifier:     BSD-3-Clause
 */
/*
-------------------------------------------------------------------------------
lookup3.c, by Bob Jenkins, May 2006, Public Domain.
-------------------------------------------------------------------------------
*/

#include <stdio.h>	/* defines printf for tests */
#include <time.h>	/* defines time_t for timings in the test */
#include <stdint.h>	/* defines uint32_t etc */
#include <odp_api.h>

#include "ofpi_hash.h"

#if (defined(ODP_BYTE_ORDER) && defined(ODP_LITTLE_ENDIAN)) && \
	ODP_BYTE_ORDER == ODP_LITTLE_ENDIAN
# define HASH_LITTLE_ENDIAN 1
# define HASH_BIG_ENDIAN 0
#elif (defined(ODP_BYTE_ORDER) && defined(ODP_BIG_ENDIAN)) && \
	ODP_BYTE_ORDER == ODP_BIG_ENDIAN
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 1
#else
# define HASH_LITTLE_ENDIAN 0
# define HASH_BIG_ENDIAN 0
#endif

#define hashsize(n) ((uint32_t)1<<(n))
#define hashmask(n) (hashsize(n)-1)
#define rot(x, k) (((x)<<(k)) | ((x)>>(32-(k))))

/*
-------------------------------------------------------------------------------
mix -- mix 3 32-bit values reversibly.

This is reversible, so any information in (a,b,c) before mix() is
still in (a,b,c) after mix().

If four pairs of (a,b,c) inputs are run through mix(), or through
mix() in reverse, there are at least 32 bits of the output that
are sometimes the same for one pair and different for another pair.
This was tested for:
* pairs that differed by one bit, by two bits, in any combination
  of top bits of (a,b,c), or in any combination of bottom bits of
  (a,b,c).
* "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed
  the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
  is commonly produced by subtraction) look like a single 1-bit
  difference.
* the base values were pseudorandom, all zero but one bit set, or
  all zero plus a counter that starts at zero.

Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
satisfy this are
    4  6  8 16 19  4
    9 15  3 18 27 15
   14  9  3  7 17  3
Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
for "differ" defined as + with a one-bit base and a two-bit delta.  I
used http://burtleburtle.net/bob/hash/avalanche.html to choose
the operations, constants, and arrangements of the variables.

This does not achieve avalanche.  There are input bits of (a,b,c)
that fail to affect some output bits of (a,b,c), especially of a.  The
most thoroughly mixed value is c, but it doesn't really even achieve
avalanche in c.

This allows some parallelism.  Read-after-writes are good at doubling
the number of bits affected, so the goal of mixing pulls in the opposite
direction as the goal of parallelism.  I did what I could.  Rotates
seem to cost as much as shifts on every machine I could lay my hands
on, and rotates are much kinder to the top and bottom bits, so I used
rotates.
-------------------------------------------------------------------------------
*/
#define mix(a, b, c) \
{ \
	a -= c;  a ^= rot(c, 4);  c += b;	\
	b -= a;  b ^= rot(a, 6);  a += c;	\
	c -= b;  c ^= rot(b, 8);  b += a;	\
	a -= c;  a ^= rot(c, 16);  c += b;	\
	b -= a;  b ^= rot(a, 19);  a += c;	\
	c -= b;  c ^= rot(b, 4);  b += a;	\
}

/*
-------------------------------------------------------------------------------
final -- final mixing of 3 32-bit values (a,b,c) into c

Pairs of (a,b,c) values differing in only a few bits will usually
produce values of c that look totally different.  This was tested for
* pairs that differed by one bit, by two bits, in any combination
  of top bits of (a,b,c), or in any combination of bottom bits of
  (a,b,c).
* "differ" is defined as +, -, ^, or ~^.  For + and -, I transformed
  the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
  is commonly produced by subtraction) look like a single 1-bit
  difference.
* the base values were pseudorandom, all zero but one bit set, or
  all zero plus a counter that starts at zero.

These constants passed:
 14 11 25 16 4 14 24
 12 14 25 16 4 14 24
and these came close:
  4  8 15 26 3 22 24
 10  8 15 26 3 22 24
 11  8 15 26 3 22 24
-------------------------------------------------------------------------------
*/
#define final(a, b, c) \
{ \
	c ^= b; c -= rot(b, 14);			\
	a ^= c; a -= rot(c, 11);			\
	b ^= a; b -= rot(a, 25);			\
	c ^= b; c -= rot(b, 16);			\
	a ^= c; a -= rot(c, 4);				\
	b ^= a; b -= rot(a, 14);			\
	c ^= b; c -= rot(b, 24);			\
}

/*
--------------------------------------------------------------------
 This works on all machines.  To be useful, it requires
 -- that the key be an array of uint32_t's, and
 -- that the length be the number of uint32_t's in the key

 The function ofp_hashword() is identical to ofp_hashlittle() on little-endian
 machines, and identical to ofp_hashbig() on big-endian machines,
 except that the length has to be measured in uint32_ts rather than in
 bytes.	 ofp_hashlittle() is more complicated than ofp_hashword() only because
 ofp_hashlittle() has to dance around fitting the key bytes into registers.
Parameters:
	k - the key, an array of uint32_t values
	length - the length of the key, in uint32_ts
	initval - the previous hash, or an arbitrary value
--------------------------------------------------------------------
*/
uint32_t ofp_hashword(const uint32_t *k,
		  size_t length,
		  uint32_t initval)
{
	uint32_t a, b, c;

	/* Set up the internal state */
	a = b = c = 0xdeadbeef + (((uint32_t)length)<<2) + initval;

	/* handle most of the key */
	while (length > 3) {
		a += k[0];
		b += k[1];
		c += k[2];
		mix(a, b, c);
		length -= 3;
		k += 3;
	}

	/* handle the last 3 uint32_t's */
	switch (length) {
	case 3:
		c += k[2]; /* fall through */
	case 2:
		b += k[1]; /* fall through */
	case 1:
		a += k[0];
		final(a, b, c); /* fall through */
	case 0:
		break; /* case 0: nothing left to add */
	}
	/* report the result */
	return c;
}


/*
--------------------------------------------------------------------
ofp_hashword2() -- same as ofp_hashword(), but take two seeds and return two
32-bit values.	pc and pb must both be nonnull, and *pc and *pb must
both be initialized with seeds.	 If you pass in (*pb)==0, the output
(*pc) will be the same as the return value from ofp_hashword().
Parameters:
	k -  the key, an array of uint32_t values
	length - the length of the key, in uint32_ts
	pc - IN: seed OUT: primary hash value
	pb - IN: more seed OUT: secondary hash value
--------------------------------------------------------------------
*/
void ofp_hashword2(const uint32_t *k,
	       size_t length,
	       uint32_t *pc,
	       uint32_t *pb)
{
	uint32_t a, b, c;

	/* Set up the internal state */
	a = b = c = 0xdeadbeef + ((uint32_t)(length<<2)) + *pc;
	c += *pb;

	/* handle most of the key */
	while (length > 3) {
		a += k[0];
		b += k[1];
		c += k[2];
		mix(a, b, c);
		length -= 3;
		k += 3;
	}

	/* handle the last 3 uint32_t's */
	switch (length) {
	case 3:
		c += k[2]; /* fall through */
	case 2:
		b += k[1]; /* fall through */
	case 1:
		a += k[0];
		final(a, b, c); /* fall through */
	case 0:
		break; /* case 0: nothing left to add */
	}
	/* report the result */
	*pc = c; *pb = b;
}


/*
-------------------------------------------------------------------------------
ofp_hashlittle() -- hash a variable-length key into a 32-bit value
  k	  : the key (the unaligned variable-length array of bytes)
  length  : the length of the key, counting by bytes
  initval : can be any 4-byte value
Returns a 32-bit value.	 Every bit of the key affects every bit of
the return value.  Two keys differing by one or two bits will have
totally different hash values.

The best hash table sizes are powers of 2.  There is no need to do
mod a prime (mod is sooo slow!).  If you need less than 32 bits,
use a bitmask.	For example, if you need only 10 bits, do
  h = (h & hashmask(10));
In which case, the hash table should have hashsize(10) elements.

If you are hashing n strings (uint8_t **)k, do it like this:
  for (i=0, h=0; i<n; ++i) h = ofp_hashlittle( k[i], len[i], h);

By Bob Jenkins, 2006.  bob_jenkins@burtleburtle.net.  You may use this
code any way you wish, private, educational, or commercial.  It's free.

Use for hash table lookup, or anything where one collision in 2^^32 is
acceptable.  Do NOT use for cryptographic purposes.
-------------------------------------------------------------------------------
*/

uint32_t ofp_hashlittle(const void *key, size_t length, uint32_t initval)
{
	uint32_t a, b, c;	/* internal state */
	/* needed for Mac Powerbook G4 */
	union { const void *ptr; size_t i; } u;

	/* Set up the internal state */
	a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;

	u.ptr = key;
	if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
		/* read 32-bit chunks */
		const uint32_t *k = (const uint32_t *)key;
#ifdef VALGRIND
		const uint8_t  *k8;
#endif

		/* all but last block: aligned reads
		   and affect 32 bits of (a,b,c) */
		while (length > 12) {
			a += k[0];
			b += k[1];
			c += k[2];
			mix(a, b, c);
			length -= 12;
			k += 3;
		}

/* handle the last (probably partial) block */
/*
 * "k[2]&0xffffff" actually reads beyond the end of the string, but
 * then masks off the part it's not allowed to read.  Because the
 * string is aligned, the masked-off tail is in the same word as the
 * rest of the string.  Every machine with memory protection I've seen
 * does it on word boundaries, so is OK with this.  But VALGRIND will
 * still catch it and complain.  The masking trick does make the hash
 * noticably faster for short strings (like English words).
 */
#ifndef VALGRIND

		switch (length) {
		case 12:
			c += k[2]; b += k[1]; a += k[0]; break;
		case 11:
			c += k[2]&0xffffff; b += k[1]; a += k[0]; break;
		case 10:
			c += k[2]&0xffff; b += k[1]; a += k[0]; break;
		case 9:
			c += k[2]&0xff; b += k[1]; a += k[0]; break;
		case 8:
			b += k[1]; a += k[0]; break;
		case 7:
			b += k[1]&0xffffff; a += k[0]; break;
		case 6:
			b += k[1]&0xffff; a += k[0]; break;
		case 5:
			b += k[1]&0xff; a += k[0]; break;
		case 4:
			a += k[0]; break;
		case 3:
			a += k[0]&0xffffff; break;
		case 2:
			a += k[0]&0xffff; break;
		case 1:
			a += k[0]&0xff; break;
		case 0:
			return c; /* zero length strings require no mixing */
		}

#else /* make valgrind happy */

		k8 = (const uint8_t *)k;
		switch (length) {
		case 12:
			c += k[2]; b += k[1]; a += k[0]; break;
		case 11:
			c += ((uint32_t)k8[10])<<16;  /* fall through */
		case 10:
			c += ((uint32_t)k8[9])<<8;    /* fall through */
		case 9:
			c += k8[8];                   /* fall through */
		case 8:
			b += k[1]; a += k[0]; break;
		case 7:
			b += ((uint32_t)k8[6])<<16;   /* fall through */
		case 6:
			b += ((uint32_t)k8[5])<<8;    /* fall through */
		case 5:
			b += k8[4];                   /* fall through */
		case 4:
			a += k[0]; break;
		case 3:
			a += ((uint32_t)k8[2])<<16;   /* fall through */
		case 2:
			a += ((uint32_t)k8[1])<<8;    /* fall through */
		case 1:
			a += k8[0]; break;
		case 0:
			return c;
		}

#endif /* !valgrind */

	} else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
		/* read 16-bit chunks */
		const uint16_t *k = (const uint16_t *)key;
		const uint8_t  *k8;

		/* all but last block: aligned reads and different mixing */
		while (length > 12) {
			a += k[0] + (((uint32_t)k[1])<<16);
			b += k[2] + (((uint32_t)k[3])<<16);
			c += k[4] + (((uint32_t)k[5])<<16);
			mix(a, b, c);
			length -= 12;
			k += 6;
		}

		/* handle the last (probably partial) block */
		k8 = (const uint8_t *)k;
		switch (length) {
		case 12:
			c += k[4]+(((uint32_t)k[5])<<16);
			b += k[2]+(((uint32_t)k[3])<<16);
			a += k[0]+(((uint32_t)k[1])<<16);
			break;
		case 11:
			c += ((uint32_t)k8[10])<<16;     /* fall through */
		case 10:
			c += k[4];
			b += k[2]+(((uint32_t)k[3])<<16);
			a += k[0]+(((uint32_t)k[1])<<16);
			break;
		case 9:
			c += k8[8];                      /* fall through */
		case 8:
			b += k[2]+(((uint32_t)k[3])<<16);
			a += k[0]+(((uint32_t)k[1])<<16);
			break;
		case 7:
			b += ((uint32_t)k8[6])<<16;      /* fall through */
		case 6:
			b += k[2];
			a += k[0]+(((uint32_t)k[1])<<16);
			break;
		case 5:
			b += k8[4];                      /* fall through */
		case 4:
			a += k[0]+(((uint32_t)k[1])<<16);
			break;
		case 3:
			a += ((uint32_t)k8[2])<<16;      /* fall through */
		case 2:
			a += k[0];
			break;
		case 1:
			a += k8[0];
			break;
		case 0:
			return c; /* zero length requires no mixing */
		}

	} else {                   /* need to read the key one byte at a time */
		const uint8_t *k = (const uint8_t *)key;

		/* all but the last block: affect some 32 bits of (a,b,c) */
		while (length > 12) {
			a += k[0];
			a += ((uint32_t)k[1])<<8;
			a += ((uint32_t)k[2])<<16;
			a += ((uint32_t)k[3])<<24;
			b += k[4];
			b += ((uint32_t)k[5])<<8;
			b += ((uint32_t)k[6])<<16;
			b += ((uint32_t)k[7])<<24;
			c += k[8];
			c += ((uint32_t)k[9])<<8;
			c += ((uint32_t)k[10])<<16;
			c += ((uint32_t)k[11])<<24;
			mix(a, b, c);
			length -= 12;
			k += 12;
		}

		/* last block: affect all 32 bits of (c) */
		switch (length) {
		case 12:
			c += ((uint32_t)k[11])<<24; /* fall through */
		case 11:
			c += ((uint32_t)k[10])<<16; /* fall through */
		case 10:
			c += ((uint32_t)k[9])<<8; /* fall through */
		case 9:
			c += k[8]; /* fall through */
		case 8:
			b += ((uint32_t)k[7])<<24; /* fall through */
		case 7:
			b += ((uint32_t)k[6])<<16; /* fall through */
		case 6:
			b += ((uint32_t)k[5])<<8; /* fall through */
		case 5:
			b += k[4]; /* fall through */
		case 4:
			a += ((uint32_t)k[3])<<24; /* fall through */
		case 3:
			a += ((uint32_t)k[2])<<16; /* fall through */
		case 2:
			a += ((uint32_t)k[1])<<8; /* fall through */
		case 1:
			a += k[0];
			break;
		case 0:
			return c;
		}
	}

		final(a, b, c);
		return c;
	}


/*
 * ofp_hashlittle2: return 2 32-bit hash values
 *
 * This is identical to ofp_hashlittle(), except it returns two 32-bit hash
 * values instead of just one.  This is good enough for hash table
 * lookup with 2^^64 buckets, or if you want a second hash if you're not
 * happy with the first, or if you want a probably-unique 64-bit ID for
 * the key.  *pc is better mixed than *pb, so use *pc first.  If you want
 * a 64-bit value do something like "*pc + (((uint64_t)*pb)<<32)".
 * Parameters:
 *	key - the key to hash
 *	length - length of the key
 *	pc - IN: primary initval, OUT: primary hash
 *	pb - IN: secondary initval, OUT: secondary hash
 */
void ofp_hashlittle2(const void *key,
		 size_t      length,
		 uint32_t   *pc,
		 uint32_t   *pb)
{
		uint32_t a, b, c; /* internal state */
		/* needed for Mac Powerbook G4 */
		union { const void *ptr; size_t i; } u;

		/* Set up the internal state */
		a = b = c = 0xdeadbeef + ((uint32_t)length) + *pc;
		c += *pb;

		u.ptr = key;
		if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
			/* read 32-bit chunks */
			const uint32_t *k = (const uint32_t *)key;
#ifdef VALGRIND
			const uint8_t  *k8;
#endif
			/* all but last block: aligned reads and
			   affect 32 bits of (a, b, c) */
			while (length > 12) {
				a += k[0];
				b += k[1];
				c += k[2];
				mix(a, b, c);
				length -= 12;
				k += 3;
			}

/* handle the last (probably partial) block */
/*
 * "k[2]&0xffffff" actually reads beyond the end of the string, but
 * then masks off the part it's not allowed to read.  Because the
 * string is aligned, the masked-off tail is in the same word as the
 * rest of the string.  Every machine with memory protection I've seen
 * does it on word boundaries, so is OK with this.  But VALGRIND will
 * still catch it and complain.  The masking trick does make the hash
 * noticably faster for short strings (like English words).
 */
#ifndef VALGRIND

			switch (length) {
			case 12:
				c += k[2]; b += k[1]; a += k[0]; break;
			case 11:
				c += k[2]&0xffffff; b += k[1]; a += k[0]; break;
			case 10:
				c += k[2]&0xffff; b += k[1]; a += k[0]; break;
			case 9:
				c += k[2]&0xff; b += k[1]; a += k[0]; break;
			case 8:
				b += k[1]; a += k[0]; break;
			case 7:
				b += k[1]&0xffffff; a += k[0]; break;
			case 6:
				b += k[1]&0xffff; a += k[0]; break;
			case 5:
				b += k[1]&0xff; a += k[0]; break;
			case 4:
				a += k[0]; break;
			case 3:
				a += k[0]&0xffffff; break;
			case 2:
				a += k[0]&0xffff; break;
			case 1:
				a += k[0]&0xff; break;
			case 0:
				/* zero length strings require no mixing */
				*pc = c; *pb = b; return;
			}

#else /* make valgrind happy */

			k8 = (const uint8_t *)k;
			switch (length)	{
			case 12:
				c += k[2]; b += k[1]; a += k[0]; break;
			case 11:
				c += ((uint32_t)k8[10])<<16;  /* fall through */
			case 10:
				c += ((uint32_t)k8[9])<<8;    /* fall through */
			case 9:
				c += k8[8];                   /* fall through */
			case 8:
				b += k[1]; a += k[0]; break;
			case 7:
				b += ((uint32_t)k8[6])<<16;   /* fall through */
			case 6:
				b += ((uint32_t)k8[5])<<8;    /* fall through */
			case 5:
				b += k8[4];                   /* fall through */
			case 4:
				a += k[0]; break;
			case 3:
				a += ((uint32_t)k8[2])<<16;   /* fall through */
			case 2:
				a += ((uint32_t)k8[1])<<8;    /* fall through */
			case 1:
				a += k8[0]; break;
			case 0:
				/* zero length strings require no mixing */
				*pc = c; *pb = b; return;
			}

#endif /* !valgrind */

		} else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
			/* read 16-bit chunks */
			const uint16_t *k = (const uint16_t *)key;
			const uint8_t  *k8;

			/* all but last block:
			   aligned reads and different mixing */
			while (length > 12) {
				a += k[0] + (((uint32_t)k[1])<<16);
				b += k[2] + (((uint32_t)k[3])<<16);
				c += k[4] + (((uint32_t)k[5])<<16);
				mix(a, b, c);
				length -= 12;
				k += 6;
			}

			/*  handle the last (probably partial) block */
			k8 = (const uint8_t *)k;
			switch (length)	{
			case 12:
				c += k[4]+(((uint32_t)k[5])<<16);
				b += k[2]+(((uint32_t)k[3])<<16);
				a += k[0]+(((uint32_t)k[1])<<16);
				break;
			case 11:
				c += ((uint32_t)k8[10])<<16; /* fall through */
			case 10:
				c += k[4];
				b += k[2]+(((uint32_t)k[3])<<16);
				a += k[0]+(((uint32_t)k[1])<<16);
				break;
			case 9:
				c += k8[8];                   /* fall through */
			case 8:
				b += k[2]+(((uint32_t)k[3])<<16);
				a += k[0]+(((uint32_t)k[1])<<16);
				break;
			case 7:
				b += ((uint32_t)k8[6])<<16;   /* fall through */
			case 6:
				b += k[2];
				a += k[0]+(((uint32_t)k[1])<<16);
				break;
			case 5:
				b += k8[4];                   /* fall through */
			case 4:
				a += k[0]+(((uint32_t)k[1])<<16);
				break;
			case 3:
				a += ((uint32_t)k8[2])<<16;   /* fall through */
			case 2:
				a += k[0];
				break;
			case 1:
				a += k8[0];
				break;
			case 0:
				/* zero length strings require no mixing */
				*pc = c; *pb = b; return;
			}

		} else { /* need to read the key one byte at a time */
			const uint8_t *k = (const uint8_t *)key;

			/* all but the last block:
			   affect some 32 bits of (a,b,c) */
			while (length > 12) {
				a += k[0];
				a += ((uint32_t)k[1])<<8;
				a += ((uint32_t)k[2])<<16;
				a += ((uint32_t)k[3])<<24;
				b += k[4];
				b += ((uint32_t)k[5])<<8;
				b += ((uint32_t)k[6])<<16;
				b += ((uint32_t)k[7])<<24;
				c += k[8];
				c += ((uint32_t)k[9])<<8;
				c += ((uint32_t)k[10])<<16;
				c += ((uint32_t)k[11])<<24;
				mix(a, b, c);
				length -= 12;
				k += 12;
			}

			/* last block: affect all 32 bits of (c) */
			switch (length) {
			case 12:
				c += ((uint32_t)k[11])<<24; /* fall through */
			case 11:
				c += ((uint32_t)k[10])<<16; /* fall through */
			case 10:
				c += ((uint32_t)k[9])<<8; /* fall through */
			case 9:
				c += k[8]; /* fall through */
			case 8:
				b += ((uint32_t)k[7])<<24; /* fall through */
			case 7:
				b += ((uint32_t)k[6])<<16; /* fall through */
			case 6:
				b += ((uint32_t)k[5])<<8; /* fall through */
			case 5:
				b += k[4]; /* fall through */
			case 4:
				a += ((uint32_t)k[3])<<24; /* fall through */
			case 3:
				a += ((uint32_t)k[2])<<16; /* fall through */
			case 2:
				a += ((uint32_t)k[1])<<8; /* fall through */
			case 1:
				a += k[0];
				break;
			case 0:
				/* zero length strings require no mixing */
				*pc = c; *pb = b; return;
			}
		}

		final(a, b, c);
		*pc = c; *pb = b;
}



/*
 * ofp_hashbig():
 * This is the same as ofp_hashword() on big-endian machines.  It is different
 * from ofp_hashlittle() on all machines.  ofp_hashbig() takes advantage of
 * big-endian byte ordering.
 */
uint32_t ofp_hashbig(const void *key, size_t length, uint32_t initval)
{
	uint32_t a, b, c;
	/* to cast key to (size_t) happily */
	union { const void *ptr; size_t i; } u;

	/* Set up the internal state */
	a = b = c = 0xdeadbeef + ((uint32_t)length) + initval;

	u.ptr = key;
	if (HASH_BIG_ENDIAN && ((u.i & 0x3) == 0)) {
		/* read 32-bit chunks */
		const uint32_t *k = (const uint32_t *)key;
#ifdef VALGRIND
		const uint8_t  *k8;
#endif
		/* all but last block:
		   aligned reads and affect 32 bits of (a,b,c) */
		while (length > 12) {
			a += k[0];
			b += k[1];
			c += k[2];
			mix(a, b, c);
			length -= 12;
			k += 3;
		}

/* handle the last (probably partial) block */
/*
 * "k[2]<<8" actually reads beyond the end of the string, but
 * then shifts out the part it's not allowed to read.  Because the
 * string is aligned, the illegal read is in the same word as the
 * rest of the string.  Every machine with memory protection I've seen
 * does it on word boundaries, so is OK with this.  But VALGRIND will
 * still catch it and complain.  The masking trick does make the hash
 * noticably faster for short strings (like English words).
 */
#ifndef VALGRIND

		switch (length) {
		case 12:
			c += k[2]; b += k[1]; a += k[0]; break;
		case 11:
			c += k[2]&0xffffff00; b += k[1]; a += k[0]; break;
		case 10:
			c += k[2]&0xffff0000; b += k[1]; a += k[0]; break;
		case 9:
			c += k[2]&0xff000000; b += k[1]; a += k[0]; break;
		case 8:
			b += k[1]; a += k[0]; break;
		case 7:
			b += k[1]&0xffffff00; a += k[0]; break;
		case 6:
			b += k[1]&0xffff0000; a += k[0]; break;
		case 5:
			b += k[1]&0xff000000; a += k[0]; break;
		case 4:
			a += k[0]; break;
		case 3:

			a += k[0]&0xffffff00; break;
		case 2:
			a += k[0]&0xffff0000; break;
		case 1:
			a += k[0]&0xff000000; break;
		case 0:
			return c;   /* zero length strings require no mixing */
		}

#else  /* make valgrind happy */

		k8 = (const uint8_t *)k;
		switch (length) {  /* all the case statements fall through */
		case 12:
			c += k[2]; b += k[1]; a += k[0]; break;
		case 11:
			c += ((uint32_t)k8[10])<<8;  /* fall through */
		case 10:
			c += ((uint32_t)k8[9])<<16;  /* fall through */
		case 9:
			c += ((uint32_t)k8[8])<<24;  /* fall through */
		case 8:
			b += k[1]; a += k[0]; break;
		case 7:
			b += ((uint32_t)k8[6])<<8;   /* fall through */
		case 6:
			b += ((uint32_t)k8[5])<<16;  /* fall through */
		case 5:
			b += ((uint32_t)k8[4])<<24;  /* fall through */
		case 4:
			a += k[0]; break;
		case 3:
			a += ((uint32_t)k8[2])<<8;   /* fall through */
		case 2:
			a += ((uint32_t)k8[1])<<16;  /* fall through */
		case 1:
			a += ((uint32_t)k8[0])<<24; break;
		case 0:
			return c;
		}

#endif /* !VALGRIND */

	} else {               /* need to read the key one byte at a time */
		const uint8_t *k = (const uint8_t *)key;

		/* all but the last block: affect some 32 bits of (a,b,c) */
		while (length > 12) {
			a += ((uint32_t)k[0])<<24;
			a += ((uint32_t)k[1])<<16;
			a += ((uint32_t)k[2])<<8;
			a += ((uint32_t)k[3]);
			b += ((uint32_t)k[4])<<24;
			b += ((uint32_t)k[5])<<16;
			b += ((uint32_t)k[6])<<8;
			b += ((uint32_t)k[7]);
			c += ((uint32_t)k[8])<<24;
			c += ((uint32_t)k[9])<<16;
			c += ((uint32_t)k[10])<<8;
			c += ((uint32_t)k[11]);
			mix(a, b, c);
			length -= 12;
			k += 12;
		}

		/* last block: affect all 32 bits of (c) */
		switch (length) {
		case 12:
			c += k[11]; /* fall through */
		case 11:
			c += ((uint32_t)k[10])<<8; /* fall through */
		case 10:
			c += ((uint32_t)k[9])<<16; /* fall through */
		case 9:
			c += ((uint32_t)k[8])<<24; /* fall through */
		case 8:
			b += k[7]; /* fall through */
		case 7:
			b += ((uint32_t)k[6])<<8; /* fall through */
		case 6:
			b += ((uint32_t)k[5])<<16; /* fall through */
		case 5:
			b += ((uint32_t)k[4])<<24; /* fall through */
		case 4:
			a += k[3]; /* fall through */
		case 3:
			a += ((uint32_t)k[2])<<8; /* fall through */
		case 2:
			a += ((uint32_t)k[1])<<16; /* fall through */
		case 1:
			a += ((uint32_t)k[0])<<24;
			break;
		case 0:
			return c;
		}
	}

	final(a, b, c);
	return c;
}
